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 37. Diaptomus laticeps, G. 0. Sars. 



(PI. LXI). 



Diaptomus laticeps, G. 0. Sars. Oversigt af de indenlandske Ferskvandscopepoder. 

 Ghr. Vid. Selsk. Forli. 18(52, p. 10. 



Specific Characters Female. Body moderately slender, with the anterior 

 division, seen dorsally, oblong in form, greatest width somewhat exceeding '/;, of 

 the length, and occurring quite in front, across the middle of the cephalosome, 

 anterior extremity broadly rounded, posterior gradually attenuated ; seen laterally, 

 considerably dilated in front, with the dorsal margin of the cephalosome boldly 

 curved. Lateral expansions of last pedigerous segment comparatively small and 

 scarcely at all extant, outer corner distinct, inner obsolete. Genital segment more 

 than twice as long as the other 2 caudal segments combined, and slightly dilated in 

 front, with a very small denticle on each side. Caudal rami fully as long as the 

 last 2 caudal segments combined, and slightly widening distally. Anterior antennae, 

 when reflexed, extending about to the base of the caudal rami. Last pair of 

 legs with a well-marked triangular projection on the hind face of 1st basal joint, 

 inner ramus very short and uniarticulate, scarcely reaching beyond the middle of 

 the 1st joint of the outer ramus, terminal joint of the latter well denned, though 

 rather small, apical spines comparatively short. Ovisac rounded. 



Male much smaller and more slender than female, resembling that of the. 

 preceding species, but somewhat more dilated anteriorly. Right anterior antenna 

 with the antepenultimate joint produced at the end anteriorly to a somewhat 

 securiform projection extending about to the middle of the penultimate joint. 

 Both legs of last pair with a small hyaline lamella inside the 2nd basal joint, 

 inner ramus well developed, acuminate, that of right leg reaching beyond the 

 middle of the distal joint of outer ramus, proximal joint of the latter produced 

 at the end outside to a remarkably strong spiniform projection, distal joint with 

 the spine of the outer edge situated about in the middle, apical claw sharply 

 curved, sub-sigmoid. Left leg extending to about the middle of the terminal 

 joint of the right, last joint produced at the end to a very narrow and elongated 

 digitiform process, and carrying inside it a still longer setiform spine. 



Colour generally bluish. 



Length of adult female reaching 1.80 mm., of male 1.40 mm. 



Remarks. This species may be easily recognized by the strongly dilated 

 cephalosome, the small size of the lateral expansions of the last pedigerous seg- 

 ment in the female, and the structure of the last pair of legs in both sexes. The 

 right anterior antenna of the male is moreover distinguished by the shape of the 

 projection of its antepenultimate joint. 



